<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>

    <script>


        // 1*2*3*4*5*...*10 
        // jc10 = jc9 * 10
        // jc9 = jc8 * 9 
        // jc8 = jc7 * 8
        // ...
        // jc1 = 1 


        function fn(n) {
            if(n === 1) return 1
            return fn(n - 1) * n 
        }
        document.write(fn(10)) ;

    </script>
    
</body>
</html>